Methylenedianiline (MDA) and/or a mixture of MDA and its higher homologues may be a feedstock used to produce methylene diphenyl diisocyanate (MDI), which in turn may be used in the synthesis of a series of polymers, for example polyurethanes, thermoplastic polymers, and epoxy resins.
Methylenedianiline may be produced from aniline or from one of its derivatives by condensation with formaldehyde in the presence of solutions of strong acids, such as hydrochloric acid, sulfuric acid, and/or phosphoric acid, to give an amine salt, which then may be neutralized with base (e.g., strong base). Thus, operating conditions required to produce a product with desired structural characteristics and without forming undesirable amounts of by-products, may require sizable quantities of strong acid. In addition, use of strong acids may necessitate use of corrosion resistant materials in the equipment. Such construction materials are often expensive. Further, neutralization of strong acids with strong bases may lead to formation of sizable quantities of salts, which must be disposed safely. These salts may also be contaminated by aromatic products, which need to be discharged, resulting in increased production costs. Additionally, substantial quantities of waste water may be generated by this process, requiring sizable processing capacity and treatment.